TheAlgorithms/Java · error · IllegalArgumentException

Invalid unit '{}'. Supported units are: {}

Error message

Invalid unit '{}'. Supported units are: {}

What it means

Thrown by TimeConverter.convertTime when either unitFrom or unitTo does not match one of the seven supported units (seconds, minutes, hours, days, weeks, months, years). Lookup is case-insensitive (lowercased via Locale.ROOT) but the string must match exactly after lowercasing. The message interpolates the offending unit and prints the full supported set.

Source

Thrown at src/main/java/com/thealgorithms/conversions/TimeConverter.java:93

            throw new IllegalArgumentException("timeValue must be a non-negative number.");
        }

        TimeUnit from = resolveUnit(unitFrom);
        TimeUnit to = resolveUnit(unitTo);

        double secondsValue = from.toSeconds(timeValue);
        double converted = to.fromSeconds(secondsValue);

        return Math.round(converted * 1000.0) / 1000.0;
    }

    private static TimeUnit resolveUnit(String unit) {
        if (unit == null) {
            throw new IllegalArgumentException("Unit cannot be null.");
        }
        TimeUnit resolved = UNIT_LOOKUP.get(unit.toLowerCase(Locale.ROOT));
        if (resolved == null) {
            throw new IllegalArgumentException("Invalid unit '" + unit + "'. Supported units are: " + UNIT_LOOKUP.keySet());
        }
        return resolved;
    }
}

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Use exact plural forms from the supported set: seconds, minutes, hours, days, weeks, months, years.
2. Normalize the unit string before calling: trim, lowercase, and map abbreviations to canonical names.
3. If you need an unsupported unit, extend the enum and UNIT_LOOKUP map or wrap the value with manual conversion.

Example fix

// before
double r = TimeConverter.convertTime(5, "min", "sec");
// after
Map<String,String> aliases = Map.of("min","minutes","sec","seconds","hr","hours","day","days");
String from = aliases.getOrDefault(unitFrom.trim().toLowerCase(), unitFrom.trim().toLowerCase());
double r = TimeConverter.convertTime(5, "minutes", "seconds");

private static final Set<String> TIME_UNITS = Set.of("seconds","minutes","hours","days","weeks","months","years");
static String normalizeTimeUnit(String u) {
    String n = u == null ? null : u.trim().toLowerCase(Locale.ROOT);
    if (!TIME_UNITS.contains(n)) throw new IllegalArgumentException("Unsupported time unit: " + u);
    return n;
}
// before convertTime:
String from = normalizeTimeUnit(unitFrom);
String to = normalizeTimeUnit(unitTo);

static boolean isValidTimeUnit(String unit) {
    return unit != null && Set.of("seconds","minutes","hours","days","weeks","weeks","months","years")
        .contains(unit.trim().toLowerCase(Locale.ROOT));
}

try {
    return TimeConverter.convertTime(value, unitFrom, unitTo);
} catch (IllegalArgumentException e) {
    // log supported units, fall back or rethrow with user-facing message
    throw new ApiException(400, "Unsupported time unit. Supported: seconds, minutes, hours, days, weeks, months, years");
}

When it happens

Trigger: Calling convertTime(value, "minutes", "miliseconds") (typo), passing a singular form like "second" instead of "seconds", passing abbreviations like "min"/"hr", or passing a non-time unit like "celsius".

Common situations: Integrating with upstream systems that emit unit abbreviations or singular forms; copy-paste errors; locale-specific unit names; assuming singular forms are accepted.

Related errors

• inputUnit must be different from outputUnit.
• timeValue must be a non-negative number.
• Unit cannot be null.
• NULL_INPUT
• UNKNOWN_WORD

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/b49afc1ac80b2641. Report an issue: GitHub.